

Per MacStories, Apple has released a new Mac OS X Lion Developer Preview 3 to its developers this evening as well as Xcode 4.1 Developer Preview 5. Apple last updated Lion for developers in late April. That version contained several UI changes presumably based on feedback from developers.
Apple is expected to discuss lion at WWDC which takes place in early June. Apple has targeted Mac OS X Lion for a summer release. No word yet on what's new in this build of Lion.
Article Link: Apple Releases Lion Developer Preview 3 and Xcode 4.1 Preview 5